The present invention creates a new advance beyond the state of the art shown in U.S. Pat. No. 5,860,262 to Frank K. Johnson (“the '262 patent”), the disclosure which is incorporated herein by reference.
Corrosion plagues all reinforced concrete structures exposed to the elements after only a few years of service reducing the load bearing capacity of a structure and imposing heavy economic burdens on the community in order to maintain them in a safe and functionally operational condition.
Another, even more costly drawback stems from the manner in which reinforced concrete facilities are constructed. A temporary wood-sheathed structure, called formwork must be fabricated on site, erected, braced, shored and tied together in order to support, contain and shape wet concrete fill for a relatively small section of the structure being built. After casting, this formwork structure must remain in place for a period of time while the wet concrete cures before being removed, cleaned, repaired and then re-erected to cast another section. These labor intensive, time consuming tasks are repeated over and over again for each incremental unit of the structure until the last cubic yard of concrete has been cast.
Vertical formwork for constructing walls must be braced and tie rods fastened to the forms to prevent them from separating when the wet concrete fill is cast into the void space. Formwork supporting horizontal slabs must be shored from underneath and the shores and formwork left in place until the concrete has gained sufficient strength to support itself before they can be removed and reused to cast another incremental section of deck or floor slab.
Concurrently with erection of the formwork, another labor-intensive, time consuming and even more costly task is taking place: rebar installation. Typically, for walls, vertical rods are installed first, one at a time. One by one, horizontal rods are then attached to the installed verticals with wires hand twisted by workers supported on the steel cage they are erecting.
The industry has made strides in reducing costs of formwork and rebar installation when constructing high rise commercial and residential buildings. Common practice in the industry is to design a building's structural steel framework and shallow reinforced concrete floor slabs as a composite structure. In such a building stay-in-place corrugated steel sheets are used to support wet concrete fill between structural members. Horizontal rebar is placed as shop-welded mats, not one at a time.
The finished concrete slab is supported on the top flanges of the wide flange structural steel members. Studs welded to the top flange protrude into the concrete slab to make the two different building materials act as a single composite structure. Composite design results in savings by requiring fewer columns, beams and connections, producing longer spans and larger rooms in buildings, and providing more flexible, and saleable floor plans. The downside of this type of construction is that the steel beams supporting composite floor slabs are exposed and must be fireproofed, another labor intensive, time consuming and costly activity.
The '262 patent discloses a panelized mold apparatus for containing, shaping and permanently encasing monolithically cast reinforced concrete walls, footings, beams and floor slabs using interlocking panel assemblies to form foundation, cavity wall and roof deck void spaces.
The perforated steel sheets used to attach parallel wall assemblies together and prevent the two sides of the cavity walls from separating during the casting process are not considered as reinforcing steel when calculating the tensile requirements for the structure. Nor are the perforated steel sheets in the footings and truss assemblies considered as reinforcement.
The '262 patent does not disclose how horizontal and vertical reinforcing steel rods are to be installed within the void spaces when the perforated sheet steel attachments are spaced at such close intervals. Nor does the patent disclose how vertical wall assemblies are to be supported against hydrostatic loads when distance between the inside and outside wall assemblies forming the void space is excessive as in the case of large dimensioned pile caps, deep deck, floor and roof slabs, foundations and piers supported on piles; nor does the '262 patent disclose how the horizontal platform assemblies are to be supported to carry gravity loads associated with casting reinforced concrete slabs over very long spans without intermediary supports or shoring.
The '262 patent does not disclose how the panelized assemblies are to be erected and rebars installed when the work site is under water. Typically, the work site must be made dry in order for the workers to erect formwork and install rebar. Making a work site dry in the middle of a body of water requires construction of a water tight enclosure, dewatering and other tasks prior to commencing concrete work, tasks that add considerable time and cost to a construction project.
It is the object of the present invention to provide a means for structurally supporting vertical and horizontal stay-in-place panelized encasement assemblies of a modular steel-framed construction mold apparatus by integrally attaching the panelized encasement assemblies to a structural steel grillage, said grillage being capable of supporting said assemblies vertically to great depths and heights, and horizontally over very long spans without recourse to external supports.
It is also an object of the present invention for the steel grillage to provide tensile strength to the permanently encased monolithic composite concrete and steel structure, thereby eliminating the necessity, and costs of installing rebar at the work site.
It is another object of the present invention to integrally attach the panelized encasement assemblies of the mold apparatus directly to structural members of the steel grillage so the two systems act as a composite unit.
It is yet another objective of the present invention to increase productivity at the construction site by pre-assembling the structural steel grillage into modular units off-site under controlled conditions.
Another object of the present invention is to pre-assemble encasement panels and connectors off-site and attach them to the grillage to form a modular unit of a steel-framed construction mold apparatus, which can be transported to the site ready for immediate installation, greatly reducing construction activity at the work site and making underwater construction of composite concrete and steel structures both practical and economical.
Another object of the present invention is to reduce the costs and facilitate construction of permanently encased monolithic composite concrete and steel structures underwater by eliminating the need for constructing temporary watertight structures typically used to create a dry work area in a submerged work site.